The present invention relates to a breather system for allowing a blow-by gas generated in a crank case of an engine to flow back into an intake system thereof.
In the prior art, a reciprocation type of engine has been provided with the breather system for allowing the blow-by gas to flow back into the intake system of the engine, which is generated by leaking out from a gap between a cylinder and a piston into a crank case. Generally, in the blow-by gas is included an oil mist which is generated by a lubrication of a chain. In the breather system, an oil component in the blow-by gas is separated, and then the gas without the oil component flows back into an air cleaner.
A conventional overhead camshaft engine is provided with a gas-liquid separation chamber within a rocker cover disposed on a cylinder head. The blow-by gas flows into the gas-liquid separation chamber through a chain chamber. Within the gas-liquid separation chamber, the oil component is separated, and then the blow-by gas is flowed back into the intake system through a blow-by passage which connects the rocker cover with the air cleaner.
For example, Japanese patent application laid-open publication No. Hei.8-74551 discloses a breather system which includes a circular breather chamber surrounding an outer periphery of a bearing of the crank shaft on one side wall of the crank case. This breather chamber is opened at an opposite side of a crank web of the crank shaft, wherein the crank web opens/closes an inlet of the breather chamber through operating together with reciprocation of the piston, i.e. a rotation of the crank shaft, thereby preventing a reverse-flow of the blow-by gas to ensure a breathing function thereof.
However, there was a problem that an oil component can not be sufficiently separated from the blow-by gas only by the gas-liquid separation chamber mounted in the rocker cover. Thus, there were caused problems that a consumption of oil is increased, a cleaner performance is apt to deteriorate since the air including oil mist flows into the air cleaner, and further a combustion performance of the engine also is affected thereby.
In particular, in the engine provided with a cylinder inclined in the gravitational direction, when the breather chamber is provided in the neighborhood of the crank shaft, a distance between the breather chamber and the air cleaner is too long, resulting in a bad layout thereof. In this case, caused was the problem also that pressure-loss of the blow-by gas is highly generated due to the long distance, so that a blow-by gas processing function is deteriorated.
An object of the present invention is to provide a breather system of an engine which can securely separate an oil component in a blow-by gas.
In order to achieve the above mentioned object, there is provided the breather system of the engine having a valve-operating device provided at a cylinder head side of the engine, driving members for driving the valve-operating device in synchronization with a crankshaft, and a driving member chamber for accommodating the driving member in the cylinder head, which comprises a gas-liquid separation chamber provided in the cylinder head apart from the driving member chamber and communicated with a crank chamber, wherein the gas-liquid separation chamber separates oil component in blow-by gas guided into from the crank chamber. In this case, the gas-liquid separation chamber may be formed along a cylinder axis direction of the engine.
According to the present invention, the breather system can be provided with the gas-liquid separation chamber for separating an oil component in the blow-by gas without adding new components and causing complication of the system construction since the gas-liquid separation chamber communicating with the crank chamber is formed in the cylinder head apart from the chain chamber. Therefore, caused are the effects that cost up can be avoided because of no added components, the oil component be securely separated, oil consumption be decreased, and a combustion performance of engine be improved. Further, even in the case of the inclined type of engine, the breather system can be provided with the gas-liquid separation chamber without losing an adequate layout thereof.
In addition, the breather chamber may be provided with a second driving member chamber for accommodating the driving member in a cylinder block, and a gas inlet having an opening for the second driving member chamber and communicated with the gas-liquid separation chamber. Thereby, the passage length of the gas-liquid separation chamber can be lengthened so as to improve the separation efficiency of oil component. In this case, the gas inlet may be opened in a surface in a side direction of the driving member within the second driving member chamber. Thereby, the droplets of oil splashed together with the movement of chain can be prevented from entering the gas inlet. Also, the gas inlet may include a surface inclined from an opening of a side of the gas-liquid separation chamber to an opening of a side of the second driving member chamber toward the crank chamber. Thereby, the oil separated from the blow-by gas in the gas-liquid separation chamber can easily flow down into the second driving member chamber via this inclined surface, and the flow of oil can be ensured even if the engine is inclined in the longitudinal direction of the crank shaft.
On the other hand, an upper end portion of the gas-liquid separation chamber may be provided with an oil flow back chamber having an opening thereof which communicates with the chain chamber. Thereby, even if the engine is inclined and a cylinder axis thereof is disposed in the substantially horizontal direction, the oil separated in the gas-liquid separation chamber can be guided into the oil flow back chamber, and then returned into the chain chamber through the opening. Further, the oil flow back chamber may include a surface inclined from an outer wall thereof to the opening, i.e. toward the crank chamber, so that the oil flowing into the oil flow back chamber can be guided into the opening along the surface to easily induce the oil into the chain chamber.